1. Field of the Invention
The present invention relates to improved mammalian GLP-1 mimetibodies, specified portions and variants specific for biologically active proteins, fragment or ligands, GLP-1 mimetibody encoding and complementary nucleic acids, host cells, and methods of making and using thereof, including therapeutic formulations, administration and devices.
2. Related Art
Recombinant proteins are an emerging class of therapeutic agents. Such recombinant therapeutics have engendered advances in protein formulation and chemical modification. Such modifications can potentially enhance the therapeutic utility of therapeutic proteins, such as by increasing half lives (e.g., by blocking their exposure to proteolytic enzymes), enhancing biological activity, or reducing unwanted side effects. One such modification is the use of immunoglobulin fragments fused to receptor proteins, such as enteracept. Therapeutic proteins have also been constructed using the Fc domain to attempt to provide a longer half-life or to incorporate functions such as Fc receptor binding, protein A binding, and complement fixation.
Diabetes is a growing epidemic that is estimated to affect over 300 million people by the year 2025 pending an effective pharmaceutical cure. Type 2 diabetes accounts for 90-95% of all cases. Complications resulting from sustained elevated plasma glucose levels include cardiovascular disease, nephropathy, neuropathy, and retinopathy. In addition, the β-cells of the pancreas die and therefore cease to secrete insulin during the later stages of type 2 diabetes. Current treatments for diabetes are associated with a variety of deleterious side effects including hypoglycemia and weight gain. In addition, current treatments for type 2 diabetes do not cure the disease but simply prolong the time until patients require insulin therapy.
Glucagon like peptide-1 (GLP-1) is a 37-amino acid peptide secreted from the L-cells of the intestine following an oral glucose challenge. A subsequent endogenous cleavage between the 6th and 7th position produces the biologically active GLP-1 (7-37) peptide. The GLP-1 (7-37) peptide sequence can be divided into 2 structural domains. The amino terminal domain of the peptide is involved in signaling while the remainder of the peptide appears to bind to the extracellular loops of the GLP-1 receptor in a helical conformation. In response to glucose, the active GLP-1 binds to the GLP-1 receptor on the pancreas and causes an increase in insulin secretion (insulinotropic action). In addition, it has been shown that GLP-1 reduces gastric emptying which decreases the bolus of glucose that is released into the circulation and may reduce food intake. These actions in combination lower blood glucose levels. GLP-1 has also been shown to inhibit apoptosis and increase proliferation of the β-cells in the pancreas. Thus, GLP-1 is an attractive therapeutic to lower blood glucose and preserve the β-cells of the pancreas of diabetic patients. In addition, GLP-1 activity is controlled by blood glucose levels. When blood glucose levels drop to a certain threshold level, GLP-1 is not active. Therefore, there is no risk of hypoglycemia associated with treatment involving GLP-1.
The viability of GLP-1 therapy has been demonstrated in the clinic. A six-week GLP-1 infusion lowered fasting and 8-hour mean plasma glucose levels effectively in type 2 diabetic patients. GLP-1 therapy also resulted in an improvement in β-cell function. Exenatide is a GLP-1 analogue currently in clinical trials. Exenatide was first identified in the saliva of the gila monster lizard, and is 53% identical to GLP-1. Exenatide can bind the GLP-1 receptor and initiate the signal transduction cascade responsible for the numerous activities that have been attributed to GLP-1 (7-37). To date, it has been shown to reduce HbA1c levels and serum fructosamine levels in patients with type 2 diabetes. In addition, it delayed gastric emptying and inhibited food intake in healthy volunteers.
However, GLP-1 is rapidly inactivated in vivo by the protease dipeptidyl-peptidase IV (DPP-IV). Therefore, the usefulness of therapy involving GLP-1 peptides has been limited by their fast clearance and short half-lives. For example, GLP-1 (7-37) has a serum half-life of only 3 to 5 minutes. GLP-1 (7-36) amide has a time action of about 50 minutes when administered subcutaneously. Even analogs and derivatives that are resistant to endogenous protease cleavage, do not have half-lives long enough to avoid repeated administrations over a 24 hour period. For example, exenatide is resistant to DPP-IV, yet it still requires twice daily preprandial dosing because of the short half-life and significant variability in in vivo pharmacokinetics. NN2211, another compound currently in clinical trials, is a lipidated GLP-1 analogue. It is expected to be dosed once daily.
Fast clearance of a therapeutic agent is inconvenient in cases where it is desired to maintain a high blood level of the agent over a prolonged period of time since repeated administrations will then be necessary. Furthermore, a long-acting compound is particularly important for diabetic patients whose past treatment regimen has involved taking only oral medication. These patients often have an extremely difficult time transitioning to a regimen that involves multiple injections of medication. A GLP-1 therapy that has an increased half-life would have a significant advantage over other GLP-1 peptides and compounds in development.
Accordingly, there is a need to provide improved and/or modified versions of GLP-1 therapeutic proteins, which overcome one more of these and other problems known in the art. The mimetibody technology provides a novel delivery platform for peptide therapeutics. A GLP-1 mimetibody may provide a means of delivering the GLP-1 peptide in a sustained manner, providing an improvement over GLP-1 peptides currently in development. Furthermore, based upon its dimeric structure and its tissue distribution characteristics, a GLP-1 mimetibody could have differentiable features with regard to insulin secretion, β-cell preservation, and food intake.